Engine/Transmission (1994 - 1998) Power Loss Problem

[chanaan7]

Hello,



I have a '95 2500 4x4 that came with my business. Apparently it has not had good towing or hill climbing abillity for over 4 years, also it only gets about 8 mpg. I think it must have a bad torque converter possibly related to the 5th wheel hitch in the bed. It shifts smoothly and the engine seemingly runs strong with good rpm and turbo response. There just is no power at the wheels. A couple of people suggested the lift pump but it seems that the injector pump would have gone out long ago if that was the case.



Any suggestions?



Thanks, '95 2500 4x4 w

 

[Joe G.]

Welcome to the TDR. I also have a '95 2500 4X4 automatic. I don't think I could get only 8 MPG on a bet. Do you have any idea what your fuel pressure is on the road? Is the engine completely stock or you don't know? Where are you? What does the ATF look like on the dip stick? Any smoke? If so what color? Does it run ok, but you are worried about kids on bicycles passing you?

 

[chanaan7]

I don't know what my fuel pressure is. The engine is stock. I live in the SF bay area. The ATF looks fine, no smoke and it runs up to highway speeds just fine. The problem is when I hit a hill it just starts loseing speed like a tired old 350 and in towing it is the same thing. Also if it is parked on a hill I have to rev it to 2K-2. 5K to get it to move.

 

[Joe G.]

The eight MPG is a puzzle. I would think that the timing had slipped to cause that, but needing 2K to get it to move points to the torque convertor instead. If the ATF looks ok, I suspect that you have one of the early aftermarket milled stator torque convertors. You could not climb a curb with one of those. Even a stock TC should not be that bad. When mine was stock it was kind of gutless, but I was getting about 15 MPG around town and 20 on the road.

 

[Joe G.]

Another question. Does the TC clutch lock up? You might try to lock out OD and see if performance improves when the TC clutch locks up.

 

[chanaan7]

I just did a TC lock up test. I was rollin at about 60 and turned off the OD then put it to the floor. It slowly climbed to 65. It seems to gain speed faster if you ease into it. Which makes me think the torque converter is not locking up. The ATF does look good but I talked to the old owner today and he just had it changed maybe a month ago.



Thanks for the help.

 

[chanaan7]

By the way, if it does turn out to be the TC, what do you recomend for an aftermarket TC.

 

[Joe G.]

That did not test lock up. Putting it to the floor would actually cause it to unlock if it was already locked. In a 47RH transmission like you have the lock up can be pretty subtle depending on tranmission condition. Start off with the OD locked out. You should feel two shifts and then a third lighter shift that you may only notice by watching the tach drop. Locking out OD eliminates a complication in the test. The normal sequence of events with OD locked out are: 1-2, 2-3, lockup. With OD on it's: 1-2, 2-3, 3-OD, lockup. Then without flooring it so it will stay locked see how it excellerates. Watch the tach to see if RPM jumps up instead of increasing steady with speed increase.



I use a DTT TC.

 

[chanaan7]

OK, I did the lock-up test. With the OD off 1-2 dropped ~200 rpm and 2-3 dropped ~100 rpm. With the OD on 1-2 and 2-3 were less noticeable but the drop from 3-4 is noticeable with over a 500 rpm drop. Does this tell you anything?

 

[Joe G.]

It sounds like your transmission is shifting properly. I don't see any indication of the TC clutch locking up from your description. There should be one more RPM drop in each case which would be the TC clutch locking up. With OD off there there should be an RPM drop after the 2-3 shift RPM drop that seems like another shift for the lockup. With OD on the lockup should happen after the 3-4 shift to OD.

 

[crabman]

C,

Send me a PM.

Look at my info on where I live.

I have a 95 and get 20 mpg around town all the time. 22+ on trips.

crabman